It's not using HTTPS, and that why its giving that warning. Any site that starts with HTTP and not HTTPS will give that warning. Did it use to use HTTPS before? You don't need to sign into the page, so I don't see it being crucial.

Nevermind, I just saw what your seeing. It's using HTTPS but when you click on "i" next to the address bar it says "Your connection to the site is not fully secure." However if I open a tab in Incognito, the same site says it's secure. Can you confirm?

It must be some kind of non-secure content used by forums.cox.com that doesn't match the certificate.